The present invention relates to video editing, and more particularly to the recording of time code in a database for manipulation during video editing.
Time code is a sequential number system representing time which is recorded onto video tape to give each frame of a video image a unique number. A description of time code is contained in ANSI/SMPTE specification 12M-1986. Time code is used within the television industry to identify a unique location of a segment of video. Editors, or edit controllers, which are computers used to edit video and audio, use the time code to uniquely identify the segment of video on video tape recorders (VTRs) that they control. There are two types of time code: Longitudinal Time Code (LTC) and Vertical Interval Time Code (VITC). LTC is time code that is recorded on a longitudinal track of a VTR, while VITC is time code that is a part of the video signal. There are also two methods of reporting time code: drop frame time code and non-drop frame time code. Drop frame time code is used when certain frames are dropped to resolve the difference between real time and color time. Real time is the time needed to transmit a black and white video signal (30 frames per second), and color time is the time needed to transmit a color video signal (29.97 frames per second). Non-drop frame time code is used in all other cases.
For edit controllers to search for a given segment of video, it is assumed that the time code is linear, i.e., time code is present and there is one frame difference in the time code between adjacent frames of video. During the video editing process segments of video are pulled together from different sources. These sources may have different time codes. As various sources are recorded to create a new video segment, the time code recorded with the video is non-linear. The video frames at the boundary between the sources do not have sequential time code. With non-linear time code editors are not able to search for video via time code because time code becomes ambiguous. To overcome ambiguity on the target media, the tape in the record VTR is striped, i.e., the color black and linear time code are recorded onto a blank tape so that it can be used with the edit controller, and the source time code is not recorded on the target media. This has the disadvantage of losing the original source material's time code.